Pothead terminal



Aug. 10, 1937. H. MILLIKEN 2,089,284

POTHEA TERMINAL Filed Aug. 4, 1953 Ill lll Patented Aug. 10, 1937 PATENTOFFICE? POTHEAD TERRIINAL Humphreys Milliken, Mount Royal, Montreal,

Quebec, Canada Application August 4, `1933, Serial No. 683,668

4 Claims.

1 or failure to properly tighten or maintain tightness of the joint,together with alternating pressure and vacuum inside the tube, due tohot and cold weather in certain cases, results in the entrance ofmoisture and breakdown of the insula- 15 tion.

After all of the parts have been assembled on the cable and the leadsheath has been wiped to the pothead body, the pot is filled with amelted bituminous compound which solidifles when cooled. It is customaryto do this filling with so the cable and terminal in an uprightposition, and for this purpose, two small holes with plugs are provided,one near the bottom of the pot and the other near the top. Theinstructions are to leave an opening-at the top of the porcelain tube 25to allow the air to escape to permit the compound to rise to the top ofthe porcelain tube so as to completely cover the paper insulation. Thisis difficult and is not-always done, one reason being that the hotliquid compound becomes chilled 3 by the relatively cool porcelain andthe compound becomes so thick that it stops the upward flow of compoundin the tube. Even though the porcelain tube is completely lled at thestart,

the compound contracts'when it cools and re tube. The sole purpose ofthe compound is to cover the insulation and prevent moisture fromentering it. Voids in the compound (especially in the upper portion ofthe tube) therefore defeat the purpose of the compound. j

My cable terminal hereinafter described eliminates such defects.

In the drawing annexed: Figure l is a vertical section View; Figure 2 isa side elevation of a device embodying my invention; and

Figure 3 is a horizontal section View on the line 3-3 of Figure 2.Referring to the drawing annexed, I is the conductor of the cable(usually stranded copper), 2 is the insulating covering (usually papertape suitably impregnated with petrolatum compound), 3 is the leadsheath, 5 is a metal pot, 55' (preferably of cast bronze) which can beef- GII fectively soldered, 6 is a porcelain tube with suitable rainshields, lis a exible diaphragm, preferably of non-corrosive metal suchas sheet copper, and having suitable corrugations to increase itsflexibility, covering a relatively large hole 8 in the side of the pot5; 9 is a clamping ring preferably of metal. Cap screws I hold the coverI in place. The contact surfaces are machined, polished or otherwisemade smooth, Y and are preferably coated with a suitable elastic 10varnish. Such a joint may be used with or without a gasket and can bereadily made impervious to moisture; furthermore the entrance of-moisture by this joint would cause no harm as will be more apparent.after considering the complete construction as hereinafter described.The porcelain tube 6 is sealed into the round hole I9 of the pot 5, bymeans of portland cement, or litharge and glycerine, which are wellknown methods, or by other suitable means, this joint beingnon-separable (except by breaking out the porcelain and replacing itwith a new porcelain). A moisture proof joint can readily be made atthis point.

On the top of the porcelain tube, a metal cap II, preferably of softcast brass (high in copper), of suitable electrical conductivity, is'permanently sealed to exclude moisture, by any of the methods abovecited.

Integral withll is a sleeve I2, there being no vent holes, nor openingsnor joints of any kind o in I-I and I2, II being sealed to the porcelainin the factory and never thereafter removed. This practically eliminatesthe possibility of moisture entering the top of the tube, there being noseparable joints as in the case of the cable terminals heretofore used.

A terminal I3, preferably of copper, is soldered to the end of theconductor I. i3 is made accurately cylindrical and smooth, to iii;closely in the bore of i2. A lug Hl is secured to i2 by a o U bolt I5and two nuts Iii, all preferably of copper.

The wall of I2 is made relatively thin, and slightly elastic so that thetightening of the U l5 bolt slightly compresses and distorts the wall ofi2 transmitting the pressure to I3, making a high-pressure electricalcontact amply capable of carrying the required current. The bare'conductor 2U is soldered into the lug IS. 0

A soft gasket I'I is used as a cushion to minlmize the strains on theporcelain due to temperature changes in the porcelain and metal cap Ii.The gasket also serves to stop the cement from running through before ithas set; it also prevents the insulating compound from running into anyminute crevice which there might be between I2 and I3.

This cable terminal is installed in the following manner: The cable iscut off the required length (within 1/2 inch is sufficiently accurate;cable terminals heretofore in use require much closer measurement). Thelead sheath and insulation are removed to the points shown. Terminal I3is soldered to conductor I. Cover 1 is removed. 'I'he entire cableterminal is slipped over the end of the cable and pushed down until theupper end of I2 comes down against the top of I3. Lug Il is clamped toI2 and tightened sufliciently to grip I3 and hold it in place. The cableterminal (and cable) are then placed in the position required on thesupporting structure (not shown). 'This may bring 5 slightly higher orlower (by less than half an inch) than the desired position on thesupporting structure. Assuming that it is not convenient to move theentire cable (which may be ft. or more in length) by this fraction of aninch, it is easier to loosen the U bolt I5 and let the cable terminalslide up or down the required amount (fraction of an inch) the slidingtaking place between I2 and I3, after which the U bolt I5 is tightenedagain gripping I3 and holding it from slipping while finishing theinstallation.

The wiped joint 4 is next made, securing the pot 5 to lead sheath 3. Thecable terminal is next removed from its supporting structure and thecable is bent over until the terminal is in a horizontal position withthe hole 8 uppermost and approximately level. The melted compound isthen poured into the pot through hole 8. As the level of the compoundrises, the hot liquid iiows freely into the entire length of theporcelain tube; in case any part of the compound cools sufficiently tothicken before reaching the far end of the porcelain, fresh liquidcompound can readily flow over the dam formed by the thickened compound,and thus reach the far end of the tube and completely cover and surroundthe paper insulation. There are no points where the air can be trappedas the level of the compound rises, all air passing freely out of thelarge hole 8. When the compound reaches the level of hole 8, pouring isstopped and time allowed for the compound4 to cool and contract, afterwhich additional compound is poured in. When the com- POund has cooledso that the contraction has practically ceased, and the level is upflush with the top of hole 8, the cover 'I is fastened in place, thecable terminal is brought upright and secured to its supportingstructure, the lug I4 is soldered to the overhead conductor IE andbolted to I2, and the job is complete.

In cold weather the compound will contract (it never becomes too hard toow slowly even in the coldest weather) and draws in the flexiblediaphragm 1 thus relieving any tendency to cause excess vacuum, and inhot Weather the reverse takes place, the diaphragm bulging out andrelieving any excessive internal pressure.

Lugs on pot 5 for bolting it to the supporting structure have beenomitted from the drawing, to avoid confusion. These lugs should belocated on thev same side as the opening 8, to facilitate bending thecable over, away from the supporting structure, into a horizontalposition, for filling, as described above.

'I'he drawing shows a terminal for a singleconductor cable. The sameconstruction is applicable to a cable having two or more conductors.

'The most common case is 'that of a cable having three conductorsinsulated from each other and encased in a single lead sheath. In suchcase a single pot or body (5) with a single opening 8, would have threeopenings I9 and three porcelain tubes 6 with three each of parts II, I2,I3, I4, I5, IE, 20.

In accordance with the provisions of the patent statutes, I have hereindescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodimentsthereof, but I desire to have it understood that the apparatus disclosedis only illustrative and that the invention can be-car ried out by othermeans.

I claim:

l. In a device of the class set forth, an insulating tube, a metalliccap permanently cemented onto the upper end thereof, an upstanding tubeformed integral with said cap and having its outer end closed by anintegral closure Wall to thereby provide a jointless metallic capstructure, the inner end of said metallic tube being open to theinterior of the insulating tube and the interior of said metallic tubebeing smooth to slidably receive the end of a conductor passing upthrough the insulating tube, said upstanding tube being slightlyyieldable transversely for distortion under external pressure appliedthereto to force the wall of said tube inwardly to thereby insure goodelectrical contact with the end of a conductor lying in said metallictube.

` 2. In a device of the class set forth, an insulating tube, a metalliccap permanently cemented onto the upper end thereof, an upstanding tubeformed integral with said cap and having its outer end closed by anintegral closure wall to thereby provide a jointless metallic capstructure, the inner end of said metallic tube being open to theinterior of the insulating tube and the interior of said metallic tubebeing smooth to slidably receive the end of a conductor passing upthrough the insulating tube, said up [standing tube being slightlyyieldable transversely for distortion under external pressure appliedthereto at opposite points on the tube to force said opposite pointsinwardly to thereby insure good electrical contact with the end of aconductor lying in said metallic tube.

3. In a device of the class set forth, an insulating tube, a metalliccap permanently cemented onto the upper end thereof, an upstanding tubeformed integral with said cap and having its outer end closed by anintegral closure wall to thereby provide a jointless metallic capstructure, the inner end of said metallic tube being open to theinterior of the insulating tube and the interior of said metallic tubebeing smooth to slidably receive the end of a conductor passing upthrough the insulating tube, said upstanding tube being slightlyyieldably trans-Jl versely for distortion under external pressureapplied thereto to force said tube wall inwardly, an insulated conductorextending through said insulating tube, and a metallic cap electricallyconnected to the said conductor and slidably fitting in said metallictube and adapted to be gripped by the Wall of said metallic tube whensaid wall is forced inwardly.

4. In a device of the class set forth, an insulating tube, a metalliccap permanently cemented onto the upper end thereof, an upstanding tubeformed integral with said cap and having its outer end closed by anintegral closure wall to thereby provide a jointless metallic capstructure, the `inner end of said metallic tube being tube. and ametallic cap electrically connected to the said conductor and slidablyfitting in said ymetallic tube and adapted to be gripped by the wall ofsaid metallic tube when said wall is forced inwardly, and insulatingmaterial filling the insulating tube, surrounding the insulatedconductor and holding it positioned therein.

HUMPHREYS M ILLIKEN.

